Nocardia zhihengii sp. nov., an actinobacterium isolated from rhizosphere soil of Psammosilene tunicoides.

A Nocardia-like actinobacterial strain, designated YIM TG2190T, was isolated from rhizosphere soil of Psammosilene tunicoides collected from Gejiu, Yunnan province, China. The cells of strain YIM TG2190T were observed to be Gram-stain positive and non-motile. The strain forms extensively branched substrate mycelia that fragments into rod-shaped elements. The 16S rRNA gene sequence analysis showed that strain YIM TG2190T is closely related to Nocardia nova (97.5%), Nocardia jiangxiensis (97.1%) and Nocardia miyunensis (96.8%). Growth occurs at 4-30 °C (optimum 28 °C), pH 6.0-8.0 (optimum pH 7.0) and the strain can tolerate NaCl (w/v) up to 3% (optimum 0-1%). The cell walls were found to contain meso-diaminopimelic acid. The whole-cell sugars were identified as glucose, mannose, ribose, galactose, arabinose and fucose. The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol mannosides, phosphatidylglycerol and an unidentified phospholipid. The menaquinones detected were MK-9 (H2) and MK-8 (H4). The major fatty acids (> 5%) were found to be C16:0 (33.9%), summed feature 3 (21.7%), C18:0 10-methyl TBSA (13.7%) and C18:1ω9c (7.0%). The DNA G+C content was determined to be 61.1 mol%. DNA-DNA relatedness between the strain YIM TG2190T and N. nova CGMCC 4.1705T, N. jiangxiensis CGMCC 4.1905T and N. miyunensis CGMCC 4.1904T were 46.9 ± 2.6, 36.8 ± 1.3, and 35.7 ± 2.6%, respectively, values which are less than the threshold value (70%) for the delineation of prokaryotic genomic species. The phenotypic, chemotaxonomic and phylogenetic data indicates that strain YIM TG2190T represents a novel species of the genus Nocardia, for which the name Nocardia zhihengii sp. nov. is proposed. The type strain is YIM TG2190T (=KCTC 39596T = DSM 100515T).